The invention relates to an illumination system for an EUV lithography device, comprising: a first facet mirror having facet elements that reflect EUV radiation, and a second facet mirror having facet elements for reflecting the EUV radiation reflected by the first facet mirror onto an illumination field of the illumination system. The invention also relates to an EUV lithography device comprising such an illumination system, and to a facet mirror comprising at least one diffractive facet element.
In illumination systems of EUV lithography devices, especially EUV projection exposure apparatuses, optical elements in the form of facet mirrors are used to generate a homogenization of the radiation generated by an EUV light source on an illumination field illuminated by the illumination system. In this case, a first facet mirror, which is also designated as field facet mirror, is typically used to generate secondary light sources in the illumination system. The second facet mirror is arranged at the location of the secondary light sources generated by the first facet mirror and is designated as pupil facet mirror. The facet elements of the second facet mirror serve for imaging the facet elements of the first facet mirror onto the illumination field. The geometry of the facet elements (e.g. square, rectangular, . . . ) of the first facet mirror therefore typically corresponds to the geometry of the illumination field.
When facet mirrors are used in EUV lithography devices, non-ideal imagings associated with light losses possibly occur on account of manufacturing errors during the production of the facet elements. What has a disadvantageous effect in this case is that the surface form of individual facet elements which is required for imaging or beam shaping cannot be produced precisely enough, or possibly can be produced only with very high expenditure, with conventional production methods.